Conventional camera modules (solid-state image sensing devices) for capturing images used in portable phones and the like are arranged such that a circuit board, a lens, and a lens holder are incorporated into a package. The circuit board includes a solid-state image sensor (CCD (charge-coupled device) or CMOS (complementary metal-oxide semiconductor) sensor IC (integrated circuits)), an infrared filter, and a terminal. The lens holder holds the lens.
It is important for these camera modules to satisfy the following two conditions: (a) an optical center of the image sensing surface of the solid-state image sensor is concentric to an optical center of the lens; and (b) the plane surface of the image sensing surface and the optical axis of the lens are orthogonal to each other.
Poor alignment precision of the lens with respect to the solid-state image sensor disables the satisfaction of these conditions. This causes problems such as images are out of focus, or images are recognized dark by the solid-state image sensor.
In response to this, the position of the lens is adjusted at the final stage of manufacture right before the camera module is shipped, so as to satisfy the conditions. The distance from the center of the lens to the image sensing surface of the solid-state image sensor (focal length) is adjusted to the image forming length of the lens in this adjustment of lens position.
However, an optical adjustment step requires high-cost investment in plant and equipment, as well as manpower. In addition, optical adjustment requires considerable skill; plenty of work hours are also required.
Furthermore, the lens holder requires a specific arrangement for optical adjustment in order to perform optical adjustment. Therefore, it is difficult to downsize the conventional camera module structurally. In addition, mass production is difficult if the lens holder is constructed by mechanical components. Moreover, material costs and the like occupy a high proportion of production costs. Consequently, production costs increase.
Patent Document 1 discloses a camera module which can easily perform optional adjustment, as illustrated in FIG. 11. In this camera module, a lens 211 is held by a lens holder 201. The lens holder 201 has contact with a glass plate 226. The glass plate 226 is arranged on the top surface of a solid-state image sensor 224 in high precision. This lens holder 201 is adhered to a circuit board 221 with an adhesive 227. This arrangement enables the optical distance (focal length) and the image forming length of the lens to be of the same length. The optical distance is the distance between the lens 211 and the solid-state image sensor 224. Thus, an optical adjusting step is not required in this arrangement.
However, this arrangement stacks an image processing device 222, the solid-state image sensor 224 and the glass plate 226 on the circuit board 221. Furthermore, the lens holder 201 is adhered to the glass plate 226. In other words, the lens holder 201 and the circuit board 221 are joined solely by the adhesive 227. Therefore, if the lens holder receives shock, problems may occur such as displacement of the lens holder 201 with respect to the circuit substrate 221, or breakage of the solid-state image sensor 224, the image processing device 222 or other components.
Patent Documents 2 and 3 disclose solid-state image sensing devices which solve this problem. The disclosed solid-state image sensing devices have a sealing section, which seals the solid-state image sensor and a transparent lid with resin. The transparent lid is sealed in such a manner that a part or whole of the transparent lid is exposed. A holder which holds the optical member is arranged to have contact with the exposed part of the transparent lid, thereby fixing an optical demarcation device to an image sensing section.
Patent Document 1
Japanese Unexamined Patent Publication, Tokukai, No. 2004-301938 (published on Oct. 28, 2004)
Patent Document 2
Japanese Unexamined Patent Publication, Tokukai, No. 2006-279533 (published on Oct. 12, 2006)
Patent Document 3
Japanese Unexamined Patent Publication, Tokukai, No. 2006-287533 (published on Oct. 19, 2006)
However, Patent Documents 2 and 3 do not disclose an arrangement in the transparent lid section to block unnecessary light from an outside. Therefore, unnecessary light from the outside finds a way inside the transparent lid section. As a result of this, malfunctions occur such as blurring of the whole photographed image, smear (bright-lines appearing vertically on the screen) appearing in the image, and glower (part of a screen hazily brightens) appearing in the image. Therefore, adequate camera functions cannot be realized.